When Simon Peter confesses Jesus as the Christ, the Son of the living God (Mt 16:16), Christ acknowledges that God the Father has revealed this precious truth to him. (17) Christ then proclaims that He will build His church upon this bedrock truth, that He Himself is the Messiah sent from God as the essence of God, and does a word-play with Peter’s name, which also means rock. (18)
Christ then promises Peter the keys of the kingdom of Heaven, declaring that whatever Peter binds or looses on Earth will be accordingly bound or loosed in Heaven. (19) Roman Catholics derive their doctrine of Apostolic Secession from this, that Peter was the first Pope, with authority to make up the rules as he goes.
But Peter was clearly not given such authority, for moments later Peter asserts himself so badly that Christ calls him Satan (23), and years later Peter is still blundering so profoundly that Paul has to rebuke him publicly for not living uprightly according to the Gospel. (Ga 2:11,14) Peter didn’t do so well when left to himself; neither would any of the rest of us.
So, it appears that the keys of the kingdom are not given to Peter as an isolated believer, but as part of a spiritual brotherhood, calling upon God in unison for Him to glorify Himself on Earth as He does in Heaven. (Mt 6:10) This is confirmed when Christ repeats this same promise to the Church: whatever they agree together to ask the Father He will do for them. (Mt 18:18-19)
This implies that the kind of alignment which moves God is a supernatural gift of mutual faith as believers seek His glory together in community. God gives no one the freedom to channel His power at their whim (1Jn 5:14-15); He promises to live through His people as they pursue His heart in supernatural unity. (2Co 6:16) For such community, grounding all truth-claims and motives in the reality of God (1Ti 3:15), nothing is impossible. (Mt 17:20)
One could also think of the keys of the kingdom of Heaven as the opportunity to open Heaven’s doors to people groups through the Gospel. Peter was the first to preach the Gospel publicly to the Jews, and the first to preach it to the Gentiles. So we could say God was giving Peter the privilege of being the one to open the door of faith to all people.